A typical type of CNC machine in the prior art used to rout, drill, saw and sand various workpieces generally consists of a base unit, a worktable mounted on such base unit, a gantry, a toolhead support assembly mounted on the gantry and a controller for controlling the operation of various movable components of the machine. The worktable may be mounted on the base unit and displaced along a longitudinal line of travel relative to the base unit, commonly referred to as the y-axis. Alternatively, the worktable may be rigidly mounted on the base unit and the gantry may be supported on and displaced relative to the base unit along the y-axis. The toolhead assembly usually is mounted on a toolhead support assembly which is mounted on a front face of a transversely disposed section of the gantry, spaced above the worktable. The toolhead support assembly is displaceable relative to the gantry along a transverse line of travel, commonly referred to as the x-axis, and the toolhead assembly is displaceable relative to the toolhead support assembly along a vertical line of travel commonly referred to as the z-axis. Displacement of such components typically is provided by a drivescrew mounted on one of such components, a follower mechanism mounted on a cooperating component, cooperable with the drivescrew, and a servomotor operated by the controller in accordance with a selected program inputted by various means into the controller.
Tools mounted on such toolhead assembly of such machines further may be provided with additional assemblies providing additional freedom of movement including a first carrier assembly rotatable about the z-axis and a second carrier assembly mounted on the first carrier assembly and rotatable about an axis perpendicular to the z-axis commonly referred to as the a-axis, further provided with a tool rotatable about an axis perpendicular to the a-axis, commonly referred to as the c-axis. The shafts of the z a-axes normally are driven by servomotors and the tool is driven by an electric motor, mounted on the toolhead assembly and operated by the controller. Such machines provided with additional freedom of movements commonly are referred to as five-axes machines.
In the proper operation of such machines, it is required that the x, y and z-axes be precisely orthogonal, and that in five-axes machines, the a-axis be perpendicular to the z-axis and the c-axis be perpendicular to the a-axis. Otherwise, a program inputted into the machine will fail to produce a part of a desired configuration with precise dimensions.
In the normal use of such machines in production, it often occurs that the toolhead assembly accidentally strikes a workpiece or fixture mounted on the worktable of such machines or another component of the machine, resulting in a misalignment of one or more of the axes of the machine, requiring recalibration of the machine. Such recalibration may require the service of a skilled technician and may be time consuming, resulting in a loss of production of the machine and correspondingly additional production costs. It therefore is desirous and the principal object of this invention to provide a means in the type of machine described for preventing a misalignment of one or more of the axes of the toolhead assembly thereof upon circumstances where such assembly accidentally strikes an object tending to cause permanent misalignment of one or more axes of the machine, requiring recalibration or in more severe circumstances, a major repair or replacement of the toolhead assembly.